Old English forca, force "pitchfork, forked instrument, forked weapon," from a Germanic borrowing (Old Frisian forke, Dutch vork, Old Norse forkr, Danish fork) of Latin furca "two-pronged fork; pitchfork; fork used in cooking," a word of uncertain origin. Old English also had forcel "pitchfork." From c. 1200 as "forked stake or post" (as a gallows or prop).
Table forks are said to have been not used among the nobility in England until 15c. and not common until early 17c. The word is first attested in this sense in English in an inventory from 1430, probably from Old North French forque (Old French furche, Modern French fourche), from the Latin word. Of rivers, from 1753; of roads, from 1839. As a bicycle part from 1871. As a chess attack on two pieces simultaneously by one (usually a knight), it dates from 1650s. In old slang, forks "the two forefingers" is from 1812.
-ful
word-forming element attached to nouns (and in modern English to verb stems) and meaning "full of, having, characterized by," also "amount or volume contained" (handful, bellyful); from Old English -full, -ful, which is full (adj.) become a suffix by being coalesced with a preceding noun, but originally a separate word. Cognate with German -voll, Old Norse -fullr, Danish -fuld. Most English -ful adjectives at one time or another had both passive ("full of x") and active ("causing x; full of occasion for x") senses.
It is rare in Old English and Middle English, where full was much more commonly attached at the head of a word (for example Old English fulbrecan "to violate," fulslean "to kill outright," fulripod "mature;" Middle English had ful-comen "attain (a state), realize (a truth)," ful-lasting "durability," ful-thriven "complete, perfect," etc.).