emphasis:  In Greek, émphasis originally meant simply ‘appearance’. It was a derivative of emphaínein ‘exhibit, indicate’, a compound verb formed from the prefix en- ‘in’ and phaínein ‘show’ (source of English phase). It came to be used as a grammatical term denoting ‘implication’ (as opposed to ‘directly expressed meaning’) and passed in this sense via Latin emphasis into English. Its main modern use, ‘special importance placed on something’, derives from the stressing of a particular word or phrase in speech to show that it is intended to imply something other than its literal meaning might seem to suggest. => phase
1570s, "intensity of expression," from Latin emphasis, from Greek emphasis "an appearing in, outward appearance;" in rhetoric, "significance, indirect meaning," from emphainein "to present, exhibit, display, let (a thing) be seen; be reflected (in a mirror), become visible," from assimilated form of en "in" (see en- (2)) + phainein "to show" (see phantasm). In Greek and Latin, originally a figure of expression implying more than would ordinarily be meant by the words, it developed a sense of "extra stress" given to a word or phrase in speech as a clue that it implies something more than literal meaning. In pure Latin, significatio.