borrowed from French mammalogie, by haplology from *mammalologie, from mammal- (base of New Latin Mammalia or French mammalien "mammalian") + -o--o- + -logie-logy — more at mammal
Note:
Perhaps introduced by the French botanist and zoologist Louis Augustin Guillaume Bosc (Bosc d'Antic) (1759-1828), who wrote the article Mammalogie in Nouveau dictionnaire d'histoire naturelle, appliquée aux arts, tome 14 (Paris, 1803), pp. 12-23. In regard to the term, Bosc comments that "On nomme ainsi, ou mieux, on doit nommer ainsi, car ce mot n'est pas encore généralement reçu, la science qui a pour objet l'étude des animaux à mamelles ou mammifères, c'est-à-dire des quadrupèdes proprement dits." ("We so designate, or rather we should designate—because this word is not yet generally accepted—the science that has as its object the study of animals with nipples, or mammifers [animals with mammary glands], that is, quadrupeds properly speaking.")
