c. 1200, "of wide application, generic, affecting or involving all" (as opposed to special or specific), from Old French general (12c.) and directly from Latin generalis "relating to all, of a whole class, generic" (contrasted with specialis), from genus (genitive generis) "stock, kind" (from PIE root *gene- "give birth, beget," with derivatives referring to procreation and familial and tribal groups).
What is common is of frequent occurrence. What is general admits of comparatively few exceptions: the general opinion (the opinion of the majority); the general welfare. [J.H.A. Günther, "English Synonyms Explained & Illustrated," Groningen, Netherlands, 1904]
Used in forming titles from late 14c. with the sense "having general authority or jurisdiction, chief." Phrase in general "without exception, in one body; as a rule, generally, not specifically" is from late 14c. General rule, one applying to an art or science as a whole, is from c. 1400. General store attested by 1810, American English, in reference to the range of goods sold; a general hospital (1737) is one not restricted to one class of persons or type of disease.
late 14c., "whole class of things or persons, a broad classification, a general truth," from general (adj.). Meaning "commander of an army" is 1570s, shortening of captain general, from French capitaine général. The English adjective was affixed to civic officer designations by late 14c. to indicate superior rank and extended jurisdiction.