Incorrect spelling, explanation: in English, there definitely are words ending in -rred, such as preferred, but there is a structural difference, between when the base word is prefer, and when it’s carry. When a word ends in a consonant such as r, it’s natural to double it. In the case of carried, y has to change to i graphically, but the pronunciation remains similar, even when you add the -ed suffix.

Correct spelling, explanation: carried is a past tense form of carry, created by adding the past tense suffix -ed. The y changes to i, because when adding ed it’s important to keep the spelling consistent with pronunciation, in this case with the suffix ie. Also, in the case of carried, the second-to-last letter would be r, and it also causes the y to become i when adding suffixes.

Definition of carried:
verb, past tense of carry
1. to support something in order to transport it
We finally carried out the sofa from the living room, but it was very heavy.
2. to keep the weight of something
The shelf carried the weight of all her books and some trophies.
3. To continue something, to uphold something (literally and figuratively)
For centuries we have carried certain traditions, such as Christmas Eve dinner.

Idioms with carried:
be carried out feet first – to get out of a situation only after death
These mountains are very dangerous; many mountaineers had been carried out of them feet first.