pitchy (adj.)

"thick, tenacious, resinous substance obtained from tar or turpentine, wood tar," late 12c., pich, piche, from Old English pic "pitch," from a Germanic borrowing (compare Old Saxon and Old Frisian pik, Middle Dutch pik, Dutch pek, Old High German pek, German Pech, Old Norse bik) of Latin pix (genitive picis) "pitch" (source of Old French poiz), from PIE root *pik- "pitch" (source also of Greek pissa (Attic pitta), Lithuanian pikis, Old Church Slavonic piklu "pitch," Russian peklo "scorching heat, hell").

The English word was improperly applied to sap from pine bark from late 14c. As a type of blackness from c. 1300. Pitch-black "as black as pitch" is attested from 1590s; pitch-dark "as dark as pitch, very dark" from 1680s.