Is there a reason for there to be so many words ending with ㅇ+이 (like 고양이, 올챙이 etc)?

Question

I´ve noticed a pattern of many words ending with ㅇ+ 이

• 고양이
• 올챙이
• 호랑이
• 달팽이

...and the list goes on. Is there any etymological reason why we have so many of these words? And is there a name for that? Also, if anyone could provide more examples of words that follow this pattern, it would be awesome!

Answer 1

이 is a syllable often associated with a person or animal in many contexts. Here are three common ways it is used.

1. suffix for a person or animal in general. => 젊은이 (youngster), 매미 (cicada), 발바리 (short-legged dog).
2. pronoun for "person". => 떠나는 이 (a person leaving), 죽은 이들 (= 죽은 사람들, the dead), 저이 (= 저 사람, that person).
3. suffix referring to a friend's/child's name if the name ends with a consonant. => 영철이 is a reference to 영철 (We rarely say just 영철 because it sounds stiff phonetically).

I believe many of the names of the animals came about by attaching 이 to a descriptive word for the animal. 고양 was probably description of the characteristic sound cats make (we hear it as a nasal sound, like 야옹, 양, 오양, etc, which probably led to 고양). 올챙이 and 달팽이 might have evolved in a similar way from a word describing them, although it is less obvious. A hundred percent obvious case is 매미 (cicada). The distinctive sound they make sounds like 맴-맴-맴-맴 to a Korean ear, so their name became 맴이 with the suffix 이 and then evolved to 매미.

호랑 in 호랑이 is hanja(Chinese character)-based, so it is a case of attaching 이 to the hanja phrase meaning "tiger".