Origin and history of transmigration

"change of residence or habitat, removal or transit from one locality to another, especially at a distance," 1610s, of persons, 1640s of animals, from Latin migrationem (nominative migratio) "a removal, change of abode, migration," noun of action from past-participle stem of migrare "to move from one place to another," probably originally *migwros, from PIE *(e)meigw- (source of Greek ameibein "to change"), which is an extended form of root *mei- (1) "to change, go, move" or perhaps a separate root. As "a number of animals migrating together" by 1880.

That European birds migrate across the seas or to Asia was understood in the Middle Ages, but subsequently forgotten. Dr. Johnson held that swallows slept all winter in the beds of rivers, while the naturalist Morton (1703) stated that they migrated to the moon. As late as 1837 the "Kendal Mercury" "detailed the circumstance of a person having observed several Swallows emerging from Grasmere Lake, in the spring of that year, in the form of 'bell-shaped bubbles,' from each of which a Swallow burst forth ...." [The Rev. F.O. Morris, "A History of British Birds," London, 1870]

"change completely, transform into some other person or thing as if by magic," 1650s, a word of unknown origin. Century Dictionary describes its usage as "humorous and contemptuous" and suggests it might be based on transform. In 17c. and 18c. it also appeared as transmography, transmigrafy. OED (1989), noting the latter, appends a note suggesting the word might be a vulgar formation based off transmigrate, which was used from c. 1600 in reference to souls passing into other bodies after death (see transmigration). If so, it might have been influenced by modify. Related: Transmogrified; transmogrifying; transmogrification (1660s).

word-forming element meaning "across, beyond, through, on the other side of; go beyond," from Latin trans (prep.) "across, over, beyond," perhaps originally present participle of a verb *trare-, meaning "to cross," from PIE *tra-, variant of root *tere- (2) "cross over, pass through, overcome" [Watkins].

Besides its use in numerous English words taken from Latin words with this prefix, it is used to some extent as an English formative .... It is commonly used in its literal sense, but also as implying complete change, as in transfigure, transform, etc. [Century Dictionary]

In chemical use indicating "a compound in which two characteristic groups are situated on opposite sides of an axis of a molecule" [Flood].

Many trans- words in Middle English via Old French arrived originally as tres-, due to sound changes in French, but most English spellings were restored later; trespass and trestle being exceptions.