c. 1200, "lacking money or resources, destitute of wealth; needy, indigent;" also "small, scanty," also voluntarily and deliberately, "devoid of possessions in conformity with Christian virtues," from Old French povre "poor, wretched, dispossessed; inadequate; weak, thin" (Modern French pauvre), from Latin pauper "poor, not wealthy," from pre-Latin *pau-paros "producing little; getting little," a compound from the roots of paucus "little" (from PIE root *pau- (1) "few, little") and parare "to produce, bring forth" (from PIE root *pere- (1) "to produce, procure").
It replaced Old English earm (from Proto-Germanic *arma-, which is of disputed origin). Late 13c. as "unfortunate, to be pitied or regretted." In contemptuous use, "morally inferior, miserable, wretched," by early 15c. Used figuratively ("spiritually poor") from early 14c. (to be poor in spirit is to be "spiritually humble"). Meaning "deficient in desirable or essential qualities" is from c. 1300. In reference to inhabited places from c. 1300; of soil, etc., from late 14c. In modest or apologetic use, "humble, slight, insignificant," from early 15c.
The poor boy sandwich, made of simple but filling ingredients, was invented and named in New Orleans in 1921. To poor mouth "deny one's advantages" is from 1965 (to make a poor mouth "whine" is Scottish dialect from 1822). Slang poor man's________ "the cheaper alternative to _______," is from 1854. Poor relation "relative or kinsman in humble circumstances" is by 1720.