The words gaiter, gator sound the same but have different meanings and spellings. Why do gaiter, gator sound the same even though they are completely different words?
The answer is simple: gaiter, gator are homophones of the English language.
A heavy cloth or leather covering for the leg extending from the instep to the ankle or knee.
A similar covering of lightweight, moisture-resistant fabric, used by skiers and hikers.
An ankle-high shoe with elastic sides.
An overshoe with a cloth top.
Informal An alligator.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.