Lyklasmiðurinn sagði að nýr lás yrði tilbúinn eftir hádegi.

Lyklasmiðurinn means the locksmith.

It is a compound:

• lykla- = a compound form related to lykill, key
• smiður = smith, maker, craftsman

So the word is literally something like key-smith.

The ending -inn is the definite article, so:

• lyklasmiður = a locksmith
• lyklasmiðurinn = the locksmith

Sagði is the 3rd person singular past tense of segja, which means to say.

So:

• segja = to say
• hann/hún sagði = he/she said

It matches the singular subject lyklasmiðurinn.

Að here means that and introduces a subordinate clause:

• Lyklasmiðurinn sagði = The locksmith said
• að nýr lás yrði tilbúinn eftir hádegi = that a new lock would be ready after noon

In English, that is often omitted:

• The locksmith said a new lock would be ready after noon

In Icelandic, að is very commonly kept.

Icelandic has no indefinite article. There is no separate word corresponding to English a/an.

So:

• nýr lás = a new lock
• lásinn = the lock

Indefiniteness is simply shown by using the noun without the definite ending.

Because nýr lás is the subject of the subordinate clause, so it is in the nominative.

Both words are masculine singular nominative:

• nýr = nominative masculine singular of nýr, new
• lás = nominative singular of lás, lock

If it were an object, you would expect a different form, for example:

• Ég pantaði nýjan lás = I ordered a new lock

So the ending -r on nýr helps show that this is the subject.

Yrði is the past subjunctive of verða.

In reported speech after a past-tense verb like sagði, Icelandic often uses this kind of form where English uses would:

• verður tilbúinn = will be ready
• yrði tilbúinn = would be ready

So:

• Nýr lás verður tilbúinn eftir hádegi = A new lock will be ready after noon
• Lyklasmiðurinn sagði að nýr lás yrði tilbúinn eftir hádegi = The locksmith said that a new lock would be ready after noon

This is a very common pattern in Icelandic indirect speech.

A natural direct-speech version would be:

Lyklasmiðurinn sagði: Nýr lás verður tilbúinn eftir hádegi.

When that is turned into indirect speech, verður becomes yrði:

Lyklasmiðurinn sagði að nýr lás yrði tilbúinn eftir hádegi.

So this is the same basic message, just reported rather than quoted directly.

Tilbúinn is an adjective meaning ready.

Here it is a predicative adjective, used after the verb yrði. Even in that position, Icelandic adjectives still agree with the noun they describe.

Since lás is masculine singular nominative, the adjective is also masculine singular nominative:

• nýr lás
• yrði tilbúinn

Compare:

• hurð is feminine, so you would get tilbúin
• verk is neuter, so you would get tilbúið

So the form tilbúinn is there because it agrees with lás.

Icelandic often has verb-second word order in main clauses, but this clause is a subordinate clause introduced by að.

After að, the order is normally:

• að + subject + finite verb + rest

So:

• að nýr lás yrði tilbúinn eftir hádegi

That is why the subject nýr lás comes before yrði.

Eftir hádegi means after noon or in the afternoon, after midday.

It is a common time expression. It usually means sometime after 12:00, not necessarily immediately after noon.

The sentence does not mean that the lock is ready by noon. It means the ready time is expected later than noon.

In many contexts, verða can mean become, but with adjectives it is often best translated more naturally as be in English.

So yrði tilbúinn can be understood literally as would become ready, but the normal English translation is:

would be ready

That is why the sentence sounds natural in English even though the Icelandic verb is verða.