The words rappel, repel sound the same but have different meanings and spellings. Why do rappel, repel sound the same even though they are completely different words?
The answer is simple: rappel, repel are homophones of the English language.
(mountaineering) a descent of a vertical cliff or wall made by using a doubled rope that is fixed to a higher point and wrapped around the body
lower oneself with a rope coiled around the body from a mountainside
to call back a <xref>hawk</xref>
cause to move back by force or influence
force or drive back
be repellent to; cause aversion in
reject outright and bluntly
Definitions from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved., from Wiktionary, Creative Commons Attribution/Share-Alike License. and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.