When Maia first started saying "yes," it was a lot closer to "ee-yah." In fact, it sounded almost exactly like my grandfather, whose speech was influenced by his Polish parents and rural life. "Ey-yah," he'd intone, when asked about whether the Cubs would win this one. It sounded odd, coming from a toddler. "Maia, do you want some yogurt with supper?" "Ey-yah," she'd reply, and I'd wonder where she picked it up, since Victor died years before she was born.
She's dropped "ey-yah" in favor of "yes," but she's also dropped "no" in favor of "nay." Again, no idea where it came from. "OK, Bugaboo, time to head up for the bath." "Nay! NAY!"