Probably from Old French rangier (“reindeer”), from Old Norse hreindýri (“reindeer”), with the suffix remodeled to -ifer.

rangifer m (genitive rangiferī); second declension

reindeer; caribou
- 1681, R. P. Iacobus Masenius, Speculum imaginum veritatis occultae‎:
  Lappones hieme cum ſuis rangiferis tranſmigrantes ex nive condenſata sibi tuguria inſtruunt, ac ſupernè ramis arborum & nive ſuper inſtrata contegunt, adverſus frigus duriſſimum ſatis muniti, quando nec alia eorum eſt veſtis, quam Rangiferorum pellis nudæ cuti aptata.
  The Lapps, migrating in winter with their reindeer, build up huts for themselves out of packed snow and covered with branches of trees on top and strewn snow, are sufficiently armed against the harshest cold, even when no other is their clothing than the pelt of their reindeer put on their naked skin.

Second-declension noun (nominative singular in -er).

More information singular, plural ...

Latin