Usually, when we change a letter in a word, it's meaning changes.
However, consider the following:
കഞ്ജബാണൻ = കഞ്ജം (കംജം = താമര) ബാണമായുള്ളവൻ = കാമദേവൻ
പഞ്ചബാണൻ = അഞ്ചു ബാണങ്ങൾ ഉള്ളവൻ = കാമദേവൻ
Strictly speaking, we changed more than one letter ( ക -> പ, ഞ്ജ -> ഞ്ച) but the sound change for the second letter change is very subtle.
Do you know other pairs of such words that keep its meaning when you change 1 (or 2, at most) letters?