felicity (n.)

late 14c., "happiness; that which is a source of happiness," from Old French felicite "happiness" (14c.), from Latin felicitatem (nominative felicitas) "happiness, fertility," from felix (genitive felicis) "happy, fortunate, fruitful, fertile," from suffixed form of PIE *dhe(i)- "to suck," with derivatives meaning "to suckle, produce, yield." Meaning "skillful adroitness, admirable propriety" is from c. 1600. A relic of Rome's origins as an agricultural community: that which brings happiness is that which produces crops. Compare pauper (see poor (adj.)) "poor, not wealthy," literally "producing little."