y/ies

[lydon]

Hello

I'm trying to find the reason why we drop the y and add the -ies in order
to make a plural noun from a singular. Such as,

hobby -> hobbies
lady -> ladies
......



I think it's somewhat related
to the pronunciation of words ending with -y but it's still hard
to draw a clear picture. Is this JUST A RULE or
does anyone know the reason.

[e2e4]

A learner

Nouns ending in y which follows a consonant form their plural by dropping the y and adding ies.

body bodies, mummy mummies, pony ponies

Nouns that end in y following a vowel form their plural by not dropping the y but adding s at the end of the word.

toy toys, galley galleys

[konungursvia]

Before the Chambers Encyclopaedia, people spelt words as they pleased. Shakespeare usually used -ie in the singular rather than -y, e.g. "a strange countrie." I suppose -ys looks too short, and resembles Tethys and other Greek names too much. So, given that -ies and -ys both existed, people preferred the former in the plural while opting for -y in the singular.

[chevalier]

Not a teacher.

It is an oversimplification, but I bet that in Middle English many of these words ended in "i" ("ladi" etc.) or "ie" ("citie"); back then the plural form was created by adding -es (-s), so it was "ladies" and "cities" respectively. Over time final "i"/"ie" has changed into "y", but the plural form has remained the same.

Btw. note that with verbs it is exactly the opposite: "-ie" becomes "-y", e.g. die-dying.