What does Boxing Day have to do with boxing?
mid-13c., "animating or vital principle in man and animals," from Old French espirit, from Latin spiritus "soul, courage, vigor, breath," related to spirare "to breathe," from PIE *(s)peis- "to blow" (cf. Old Church Slavonic pisto "to play on the flute").
Original usage in English mainly from passages in Vulgate, where the Latin word translates Greek pneuma and Hebrew ruah. Distinction between "soul" and "spirit" (as "seat of emotions") became current in Christian terminology (e.g. Greek psykhe vs. pneuma, Latin anima vs. spiritus) but "is without significance for earlier periods" [Buck]. Latin spiritus, usually in classical Latin "breath," replaces animus in the sense "spirit" in the imperial period and appears in Christian writings as the usual equivalent of Greek pneuma.
Meaning "supernatural being" is attested from c.1300 (see ghost); that of "essential principle of something" (in a non-theological sense, e.g. Spirit of St. Louis) is attested from 1690, common after 1800. Plural form spirits "volatile substance" is an alchemical idea, first attested 1610; sense narrowed to "strong alcoholic liquor" by 1670s. This also is the sense in spirit level (1768).
1590s, "to make more active or energetic" (of blood, alcohol, etc.), from spirit (n.). The meaning "carry off or away secretly" (as though by supernatural agency) is first recorded 1660s.
spirit spir·it (spĭr'ĭt)
spirits An alcohol solution of an essential or volatile substance.
spirits An alcoholic beverage, especially distilled liquor.
A liquid that has been distilled.
(Heb. ruah; Gr. pneuma), properly wind or breath. In 2 Thess. 2:8 it means "breath," and in Eccl. 8:8 the vital principle in man. It also denotes the rational, immortal soul by which man is distinguished (Acts 7:59; 1 Cor. 5:5; 6:20; 7:34), and the soul in its separate state (Heb. 12:23), and hence also an apparition (Job 4:15; Luke 24:37, 39), an angel (Heb. 1:14), and a demon (Luke 4:36; 10:20). This word is used also metaphorically as denoting a tendency (Zech. 12:10; Luke 13:11). In Rom. 1:4, 1 Tim. 3:16, 2 Cor. 3:17, 1 Pet. 3:18, it designates the divine nature.