"coniferous tree, tree of the genus Pinus," Old English pin (in compounds), from Old French pin and directly from Latin pinus "pine, pine-tree, fir-tree," which is perhaps from a PIE *pi-nu-, from root *peie- "to be fat, swell" (see fat (adj.)).
If so, the tree's name would be a reference to its sap or pitch. Compare Sanskrit pituh "juice, sap, resin," pitudaruh "pine tree," Greek pitys "pine tree." Also see pitch (n.1). The native Old English word was furh (see fir). Pine-top "cheap illicit whiskey," is attested by 1858, Southern U.S. slang.
Most of us have wished vaguely & vainly at times that they knew a fir from a pine. As the Scotch fir is not a fir strictly speaking, but a pine, & as we shall continue to ignore this fact, it is plain that the matter concerns the botanist more than the man in the street. [Fowler]
Middle English pinen "cause to starve" (c. 1300), from Old English pinian "to torture, torment, afflict, cause to suffer," from *pīn (n.) "pain, torture, punishment," from a general Germanic word (compare Middle Dutch pinen, Old High German pinon, German Pein, Old Norse pina), all possibly ultimately from Latin poena "punishment, penalty" (see penal). If so, the Latin word probably came into Germanic with Christianity.
The intransitive sense of "to languish, waste away, be consumed with grief or longing," the main modern meaning, is recorded from early 14c., via the Middle English intransitive senses of "endure penance, torment oneself; endure pain, suffer." Related: Pined; pining.