"nacreous inner layer of the shell of various bivalve mollusks," c. 1500, translating Medieval Latin mater perlarum, with the first element perhaps connected in popular imagination with obsolete mother (n.2) "dregs." Compare Italian madreperla, French mère-perle, Dutch parelmoer, German Perlmutter, Danish perlemor. It is the stuff of pearls but in a layer instead of a mass.
late 14c., Latin, literally "nurturing mother," a title given by Romans to certain goddesses, especially Ceres and Cybele, from alma, fem. of almus "nourishing," from alere "to nourish, rear, support, maintain" (from PIE root *al- (2) "to grow, nourish") + māter "mother" (see mother (n.1)). In sense of "one's university or school," attested from 1710.
"tough outer membrane surrounding the brain and the spinal cord," c. 1400, from Medieval Latin dura mater cerebri, literally "hard mother of the brain," a loan-translation of Arabic umm al-dimagh as-safiqa, literally "thick mother of the brain." "In Arabic, the words 'father,' 'mother,' and 'son' are often used to denote relationships between things" [Klein].
"occasion on which entertainment or profit is derived from injury or death of another," 1860, originally in reference to holidays for gladiatorial combat; the expression seems to be entirely traceable to an oft-quoted passage on a dying barbarian gladiator from the fourth canto (1818) of Byron's "Childe Harold's Pilgrimage":
But where his rude hut by the Danube lay
There were his young barbarians all at play,
There was their Dacian mother. He, their sire,
Butcher'd to make a Roman holiday!
