If papa is a stand-in for father, I'd pronounce it with a long a, as in father. If papa is a stand-in for grandfather, I'd pronounce the first a as in apple, an

If papa is a stand-in for father, I'd pronounce it with a long a, as in father. If papa is a stand-in for grandfather, I'd pronounce the first a as in apple, and the second as in paw. But of also spell it papaw. Seeing 'pa' in its own, I'd never think it was pronounced like paw, unless I was reading something written in Hungarian.