From mer- + baby.
merbaby (plural merbabies)
- A baby mermaid or merman.
1997, Elizabeth Lane, The Tycoon and the Townie[1], Harlequin, →ISBN:"She should have stayed in the ocean where she belonged. She could have married some nice young merman and had some cute little merbabies and lived a long, happy life—"
2003, Liz Kessler, The Tail of Emily Windsnap, Scholastic, →ISBN, page 57:There were mermaids with gold chains around slinky long tails, swimming along with little merchildren. One had a merbaby on her back, the tiniest little pink tail sticking out from under its sling.
2009, Penny Kendal, Merbaby, Evans Brothers Limited, →ISBN, page 35:But Anna held the merbaby tight and carried her towards the sea.