Etymology

The echidna sense is derived from the verb form, English settlers in Australia would puggle to get rabbits out of holes and sometimes find an echidna. (Reference: Echidnas, Australian Broadcasting Commission Radio National Science Show, 11 November 2000, transcript.)
The canine sense is derived from the parent breed names (Reference: http://www.puggle.org)

Noun

1. A baby monotreme.
2. A small mixed breed of dog created by mating a pug and beagle