also in-door, 1670s, opposed to outdoor, contracted from within door; the form indoors is attested from 1759 (within-doors is from 1750); as an adverb from 1801.
1830, noun use of neuter of Latin aquarius "pertaining to water," as a noun, "water-carrier," genitive of aqua "water" (from PIE root *akwa- "water"). The word existed in Latin, but there it meant "drinking place for cattle." Originally especially for an artificial pond growing aquatic plants; of indoor "ocean gardens" by 1853. The Victorian mania for indoor aquariums began with the book "The Aquarium," published 1854 by English naturalist Philip Henry Gosse. An earlier attempt at a name for "fish tank" was marine vivarium.
a type of woman's indoor cap with a bag-shaped crown and a broad band and frills, 1795 (as simply mob, 1748), from cap (n.) + obsolete mob (n.) "negligent attire" (1660s), earlier "a strumpet" (earlier form mab, 1550s), which is related to the obsolete verb mob "to tousle the hair, to dress untidily" (1660s), and perhaps is ultimately from mop (n.), but has been influenced by Mab as a female name. Dutch has a similar compound, mopmuts, but the relationship between it and the English word is uncertain.
As a trademark name for toys made of foam-like material for indoor play, introduced 1970 (Nerf ball). By 1995 this had yielded a verbal sense of "to make less effective" (as a Nerf basketball is softer and lighter than the real thing).
The Cucking-stool was a means adopted for the punishment of scolds and incorrigible women by ducking them in the water, after having secured them in a chair or stool, fixed at the end of a long pole, serving as a lever by which they were immersed in some muddy or stinking pond. [Willis's Current Notes, February 1851]
early 13c., from verbal noun from cuck "to void excrement," from Old Norse kuka "feces," from PIE root *kakka- "to defecate." So called because they sometimes resembled the old close stool of the pre-plumbing days, a portable indoor toilet that looked like a chair with a box under the seat. Old folk etymology made the first element a corruption of cotquean. For second element, see stool. Also known as trebucket and castigatory, it was used on fraudulent tradesmen, in addition to disorderly women, either for public exposure to ridicule or for ducking.