Where did the Sergeant pronunciation come from?

My mom sent me an old video from my basic encampment, both my parents (Former army) were so confused about the “Yes Saarrrrrrrgeant!” pronunciation of NCO ranks, comparing them to Tony the tigers “Their grrrrreat!” I was just wondering, is there any actual heritage to that or is it just another random CAP-ism like raising you right fist at 90 degrees?