My daughter calls it mummymilk. This evolved from "mu" at 7-8
months, to "mite" at 9 months, "muk" at 10 months and
"mummy-mummy-yummy-yummy" at 13 months. We always just said "milk".
The more interesting term she coined was "daddymilk" referring to
cow's milk (as in, what she got when I wasn't around) at around 14-15
months.
Jennifer Landels, BA, CE
Vancouver BC