eojeneun gwigeorireul ilheobeorilkka bwa gabang ane neoheo dwosseo.

The -는 here is a topic marker. 어제는 means something like as for yesterday or yesterday, at least.

In this sentence, -는 helps set the time frame as the topic of what follows. It can also give a slight contrastive feeling depending on context, such as:

• 어제는 I did this...
• maybe implying today is different

If you just said 어제, the sentence would still be natural. Adding -는 simply gives a little more structure and emphasis to yesterday as the topic.

Yes, 귀걸이 usually means earring or earrings, depending on context. Korean nouns generally do not have to show singular vs. plural the way English does.

So 귀걸이를 잃어버릴까 봐 can mean:

• because I was worried I might lose my earring
• or because I was worried I might lose my earrings

The particle -를 / -을 marks 귀걸이 as the object of the verb.

If someone really wanted to emphasize plural, they could sometimes say 귀걸이들을, but in normal speech that often sounds unnecessary.

Both relate to losing something, but 잃어버리다 is more common when talking about accidentally losing an object.

• 잃다 = to lose
• 잃어버리다 = to lose, often with a stronger sense of ending up losing it or losing it by mistake

So:

• 길을 잃다 = to lose one’s way
• 물건을 잃어버리다 = to lose an item

In this sentence, 귀걸이를 잃어버릴까 봐 sounds very natural because it is about possibly misplacing or losing an earring.

-ㄹ까 봐 / -을까 봐 expresses worry, concern, or precaution about something that might happen.

So 잃어버릴까 봐 means:

• because I was worried I might lose it
• for fear that I might lose it
• in case I lost it or more naturally in case I might lose it

It is often used when someone takes action to prevent something undesirable:

• 비 올까 봐 우산을 가져왔어.
  I brought an umbrella because I thought it might rain.

• 늦을까 봐 일찍 출발했어.
  I left early because I was worried I might be late.

So in your sentence, putting the earrings in the bag was the precaution.

Because the speaker is describing a past worry about a possible future event.

From the point of view of yesterday, the speaker was thinking:

• I might lose my earrings

That possible loss had not happened yet at that moment, so Korean uses the prospective form 잃어버릴.

So the timeline is:

1. Yesterday
2. the speaker worried I might lose the earrings
3. so the speaker put them in the bag

This is very natural in Korean. The final action is in the past, but the feared event is still expressed as a possibility from that past moment.

가방 안에 means inside the bag.

Breakdown:

• 가방 = bag
• 안 = inside
• 에 = location/destination marker

Here, 에 is used because the earrings were put into that place.

• 가방 안에 넣다 = to put something inside the bag

If you used 에서, that usually marks the place where an action happens, not the destination/location of the object in this kind of sentence.

So:

• 가방 안에 넣었어 = I put it inside the bag
• not 가방 안에서 넣었어 in this context

넣어 두다 means to put something somewhere and leave it there for later, often with a sense of preparation, convenience, or precaution.

So:

• 넣었어 = I put it in
• 넣어 뒀어 = I put it in and left it there / I had put it in there

In this sentence, 넣어 뒀어 is especially appropriate because the action was done on purpose to prevent losing the earrings.

It gives the feeling of:

• I stored them there
• I put them there and kept them there
• I set them aside in the bag

This works very well with 잃어버릴까 봐, because the speaker is taking precautionary action.

넣어 뒀어 is a contracted spoken form of 넣어 두었어.

The verb is:

• 두다 → 두었어 in past form
• in everyday speech, 두었어 often contracts to 뒀어

So:

• 넣어 두었어 = full form
• 넣어 뒀어 = common spoken contraction

Both are correct, but 넣어 뒀어 sounds more natural in casual conversation.

You will see the same thing in other verbs too:

• 해 두었어 → 해 뒀어
• 써 두었어 → 써 뒀어

Korean often leaves out subjects when they are obvious from context.

In English, you usually need to say I:

• I put them in my bag because I was worried I might lose them.

In Korean, if the speaker is clearly talking about their own action and feelings, the subject is usually omitted.

So this sentence naturally implies:

• I was worried
• I put them in the bag

You could add 내가 if you really wanted to emphasize the subject, but it would usually sound unnecessary here.

Not exactly. It is closer to:

• because I was worried that...
• for fear that...
• in case...

A plain because in Korean is often -아서/어서 or -기 때문에, but -까 봐 specifically includes the idea of uncertainty and concern about a possible situation.

Compare:

• 비가 와서 우산을 썼어.
  I used an umbrella because it rained.

• 비 올까 봐 우산을 가져갔어.
  I took an umbrella because I thought it might rain.

So -까 봐 is not just cause; it is cause based on worry or precaution.

The ending -어 / -아 / -었어 is informal, casual speech. Here, 뒀어 is a casual past-tense ending.

That means the speaker is talking to:

• a friend
• someone younger
• someone they are close to
• or in a casual context

More polite versions would be:

• 어제는 귀걸이를 잃어버릴까 봐 가방 안에 넣어 뒀어요.
• or less contracted: 넣어 두었어요

So the sentence itself is not rude; it is just casual.

Most of the time, -까 봐 is used when the speaker is worried about something undesirable or uncertain. That is why it often appears with precautionary actions.

Examples:

• 늦을까 봐 택시를 탔어.
  I took a taxi because I was worried I’d be late.

• 감기 걸릴까 봐 따뜻하게 입었어.
  I dressed warmly because I was worried I might catch a cold.

It is much more natural with concerns, risks, or negative possibilities than with clearly positive outcomes.

A useful breakdown is:

• 어제는 = as for yesterday
• 귀걸이를 = the earring(s)
• 잃어버릴까 봐 = because I was worried I might lose them
• 가방 안에 = inside the bag
• 넣어 뒀어 = I put them and left them there / I had put them there

So the logic is:

1. a possible problem: I might lose my earrings
2. a preventive action: I put them inside my bag
3. time frame: yesterday

That order is very natural in Korean: reason or concern first, action later.