animalcule

Learned borrowing from Late Latin animalculum (“lowly or small animal”) + English -cule (diminutive suffix). Animalculum is derived from Latin animal (“animal; living creature”) + -culum (diminutive suffix); and animal from animāle, the nominative neuter singular of animālis (“animate, living; relating to living creatures”), from anima (“breath; life; soul, spirit”) (ultimately from Proto-Indo-European *h₂enh₁- (“to breathe”)) + -ālis (suffix forming adjectives of relationship). The English word is analysable as animal +‎ -cule.