The words babble, babel sound the same but have different meanings and spellings. Why do babble, babel sound the same even though they are completely different words?
The answer is simple: babble, babel are homophones of the English language.
To utter a meaningless confusion of words or sounds: Babies babble before they can talk.
To talk foolishly or idly; chatter: "In 1977 [he] was thought of as crazy because he was babbling about supply side” ( Newt Gingrich).
To make a continuous low, murmuring sound, as flowing water.
To utter rapidly and indistinctly.
A confusion of sounds or voices. See Synonyms at noise.
A scene of noise and confusion.
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.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").