Caleb's first word: uh-oh

Caleb's been talking a lot lately - but I've had trouble distinguishing any clear words.  Every once in a while he'll say a bunch of stuff altogether and I'll say "yeah!" and he looks at me like I've lost my mind and I wonder what I've just said yes to ...

... but his first clearly distinguishable word is beyond a doubt "uh-oh."  He even uses it appropriately, like after spilling half of a box of raisins on the floor.  It usually sounds more like "yuh-go" but it's very clearly "uh-oh!"