ogre n.

"a female ogre," 1713; see ogre + -ess.

"ogre, devouring monster," 1590s, perhaps a reborrowing of the same word that became Old English orcþyrs, orcneas (plural), which is perhaps from a Romanic source akin to ogre, and ultimately from Latin Orcus "Hell," a word of unknown origin. Also see Orca. Revived by J.R.R. Tolkien (1892-1973), who might have got it from Beowulf, as the name of a brutal race in Middle Earth.

But Orcs and Trolls spoke as they would, without love of words or things; and their language was actually more degraded and filthy than I have shown it. ["Return of the King," 1955]

word-ending that sometimes distinguish British from American English. In the U.S., the change from -re to -er (to match pronunciation) in words such as fibre, centre, theatre began in late 18c. and became standard there over the next 25 years at the urging of Noah Webster (the 1804 edition of his speller, and especially his 1806 dictionary). The -re spelling, like -our, however, had the authority of Johnson's dictionary behind it and was unmoved in Britain, where it came to be a point of national pride, contra the Yankees.

Despite Webster's efforts, -re was retained in words with -c- or -g- (such as ogre, acre, the latter of which Webster insisted to the end of his days ought to be aker, and it was so printed in editions of the dictionary during his lifetime). The -re spelling generally is more justified by conservative etymology, based on French antecedents. It is met today in the U.S. only in Theatre as an element in the proper names of entertainment showplaces, where it is perhaps felt to inspire a perception of bon ton.