What's the "een" in Halloween?
1580s, from Spanish mosquito "little gnat," diminutive of mosca "fly," from Latin musca "fly," from PIE root *mu- "gnat, fly," imitative of insect buzzing (cf. Sanskrit maksa-, Greek myia, Old English mycg, Modern English midge, Old Church Slavonic mucha), perhaps imitative of the sound of humming insects.
mosquito mos·qui·to (mə-skē'tō)
n. pl. mos·qui·toes or mos·qui·tos
Any of various two-winged insects of the family Culicidae, in which the female of most species has a long proboscis for sucking blood. Some species are vectors of diseases such as malaria and yellow fever.