21 month old repeating made up word over and over

[Hitchyhero]

My little one just repeats over and over the phrase 'aahhhhdahhhhh' and it really is beginning to drive me had.

Since he's tried to start speaking.... That is all he has ever said. I occasionally attempts other words (Christmas tree, dinosaur ' but his default word is ahhhhdahhh.

If he wants something he will say aahhdahhh. I've tried encouraging him to say the word first until I give it him. For example, if he wants to get up on the sofa or for me to pick him up, I encourage him to say sofa or pick up. He does repeat it but it's been months and still his default is aahhdahhh.

I know he knows more than he speaks because if I give him any instructions he follows them perfectly. But I'm hearing aaaahhdahhhhh 10 times a minute from morning till night. It's driving me crazy.

I can't even think of where aahhhh dahhhh has come from. It doesn't sound like anything we've said. But he uses the word for everything.

My 2 year old does this. It was baaah and now its doh. I'm guessing/hoping it's normal. He can say and identify all his colours and can count to 4, but only has about 60 words altogether. He also sits and speaks gibberish, rather than any understandable words. I am guessing this is all normal.