c. 1300, fantum, famtome, "illusion, unreality; an illusion," senses now obsolete, from Old French fantosme (12c.), from Vulgar Latin *fantauma, from Latin phantasma "an apparition," from Greek phantasma "image, phantom, apparition; mere image, unreality," from phantazein "to make visible, display," from stem of phainein "to bring to light, make appear," from PIE root *bha- (1) "to shine." The ph- was restored in English late 16c. (see ph).
Meaning "a specter, spirit, ghost" is attested from late 14c.; that of "something having the form, but not the substance, of a real thing" is from 1707. As an adjective from early 15c. (Coleridge used phantomatic for "phantom-like, unreal"). Phantom limb "sensation of the presence of an amputated arm or leg" is attested by 1871.
"part or member," Old English lim "limb of the body; any part of an animal body, distinct from the head and trunk;" main branch of a tree," from Proto-Germanic *limu- (source also of Old Norse limr "limb," lim "small branch of a tree"), a variant of *lithu- (source of Old English liþ, Old Frisian lith, Old Norse liðr, Gothic liþus "a limb;" and with prefix ga-, source of German Glied "limb, member").
The unetymological -b began to appear late 1500s for no etymological reason (perhaps by influence of limb (n.2)). The Old English plural was often limu; limen and other plural forms in -n lasted into Middle English. Since c. 1400 especially of a leg; in Victorian English this usage was somewhat euphemistic, "out of affected or prudish unwillingness to use the word leg" [Century Dictionary]. However in Old and Middle English, and until lately in dialects, it could mean "any visible body part":
The lymmes of generacion were shewed manyfestly. [Caxton, "The subtyl historyes and fables of Esope, Auyan, Alfonce, and Poge," 1484]
Hence, limb-lifter "fornicator" (1570s). Limb of the law was 18c. derisive slang for a lawyer or police officer. To go out on a limb in figurative sense "enter a risky situation" is from 1897. Alliterative life and limb in reference to the body inclusively is from c. 1200. Obsolete limb-meal (adv.) "limb-from-limb, piecemeal" is from late Old English lim-mælum.
genetic disorder causing developmental and intellectual delays, 1961, from J.L.H. Down (1828-1896), English physician; chosen as a less racist name for the condition than earlier mongolism.
1981, named for the sake of Austrian pediatrician Hans Asperger (1906-1980), who described it in 1944 (and called it autistic psychopathy; German autistischen psychopathen). A standard diagnosis since 1992; recognition of Asperger's work was delayed, perhaps, because his school and much of his early research were destroyed by Allied bombing in 1944.
The example of autism shows particularly well how even abnormal personalities can be capable of development and adjustment. Possibilities of social integration which one would never have dremt of may arise in the course of development. [Hans Asperger, "Autistic psychopathy in Childhood," 1944]