pine-tree (n.)

"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]

Old English treo, treow "tree" (also "timber, wood, beam, log, stake"), from Proto-Germanic *trewam (source also of Old Frisian tre, Old Saxon trio, Old Norse tre, Gothic triu "tree"), from PIE *drew-o-, suffixed variant form of root *deru- "be firm, solid, steadfast," with specialized senses "wood, tree" and derivatives referring to objects made of wood.

The line which divides trees from shrubs is largely arbitrary, and dependent upon habit rather than size, the tree having a single trunk usually unbranched for some distance above the ground, while a shrub has usually several stems from the same root and each without a proper trunk. [Century Dictionary]

In Old English and Middle English also "thing made of wood," especially the cross of the Crucifixion and a gallows (such as Tyburn tree, famous gallows outside London). Middle English also had plural treen, adjective treen (Old English treowen "of a tree, wooden"). For Dutch boom, German Baum, the usual words for "tree," see beam (n.).

Meaning "framework of a saddle" is from 1530s. Meaning "representation of familial relationships in the form of a tree" is from c. 1300. Tree-hugger, contemptuous for "environmentalist" is attested by 1989.

Minc'd Pyes do not grow upon every tree,

But search the Ovens for them, and there they be.

["Poor Robin," Almanack, 1669]