[mosquito]. From the Spanish. The word is the diminutive of the Latin "musca," a fly.
[scruple]. From the Latin "scrupulus," a small sharp stone. This word meant first in English a very small weight of twenty grains; then it came to mean a slight weight on the mind or conscience. In the Trial Scene of Shakespeare's Merchant of Venice we have the original sense used,—"the twentieth part of one poor scruple."
[exuberant]. From the Latin "uber," udder. Thus it comes to mean "flowing from the udder" and so "overflowing."
[handkerchief]. "Kerchief" came from two French words "couvre," to cover, and "chef," the head. It meant a head cloth. Then a smaller cloth was used in the hand and this was called a hand-kerchief.
[lunacy]. From the Latin "luna," the moon. In former times Europeans used to think that madness was due to some influence of the moon. Compare the word moonstruck.
[algebra]. This is one of the many words from Arabic beginning with "al," the. Compare alkali, albatross, alcohol, alembic, alchemy, alcove.
[Euclid]. This word was originally the name of a great Greek mathematical writer. His writings were called "Books of Euclid." Now the subject is usually called Geometry.
[absurd]. From the Latin "surdus," deaf. Deaf people generally appear stupid to those who can hear. So this word has come to mean foolish or ridiculous.
[topsy-turvy]. This probably is a shortened form of topside-turvy,—"turvy" being a colloquial corruption for "turned" or "turned over."