c. 1300, title of honor of a knight or baronet (until 17c. also a title of priests), variant of sire, originally used only in unstressed position. Generalized as a respectful form of address by mid-14c.; used as a salutation at the beginning of letters from early 15c. Not an acronym of anything.

masc. proper name, Old English Ælfræd, literally "elf-counsel," from ælf (see elf) + ræd "counsel" (see rede). Alfred the Great was king of the West Saxons 871-899. Related: Alfredian (1814).

transuranic element, 1957, named for Alfred Nobel (q.v.). With metallic element ending -ium.

1620s, in Spanish use, "a gentleman;" in address, "sir;" from Spanish señor "a gentleman; sir," from Medieval Latin senior "a lord," a special use of Latin senior "elder" (source also of Portuguese senhor), accusative of senior "older" (from PIE root *sen- "old").

"supercontinent of the late Paleozoic era," 1924, from Greek pan- "all" (see pan-) + gaia "earth" (see Gaia). First attested in German, 1920, in Alfred Wegener's "Die Entstehung der Kontinente und Ozeane" (but according to OED the word is not found in 1914 first edition).

unit of force, 1904, named in honor of Sir Isaac Newton (1642-1727). Related: Newtonian.

intelligence test, first published 1916 as a revision and extension of the Binet-Simon intelligence tests, from Stanford University (California, U.S.) + the name of French psychologist Alfred Binet, who devised the attempt at a scientific measurement of intelligence.