Bit of a Potty mouth!!

So some how Kahtrell has picked up a coupld naughty words (I'm thinking from the ILs as DP and I very rarely swear......I mean I still spell the words out rather than say them lmfao). Anywhos every so often I'll hear a little......"oh sh!t" or "f**K". Reprimanding him for saying it makes it worse..and he'll constantly repeat it! if I tell him not too.
Any suggestions??. At the mo I'm trying to divert him by saying another word when he swears.....sometimes he'll say "oh gosh"...so I guess that's something!!...just gotta keep at it.

We weren't allowed to say "sucks"...... ie "homework sucks"

DH often forgets that little people have large flappy ears so we get it fairly often. When she says it I say something about blue knickers and she happily goes off repeating that.

lol, yea I'm trying to ignore it, or say another word to try and send him in a different direction!!, works about half of the time. Hard not to laugh though cos though it's naughty it sounds cute lolz. Just fingers crossed he doesn't say it at daycare!