Is it ensure, insure, or assure?
1570s, buffe leather "leather made of buffalo hide," from Middle French buffle "buffalo" (15c., via Italian, from Latin bufalus; see buffalo (n.)).
The color term comes from the hue of buffalo hides (later ox hides). Association of "hide" and "skin" led c.1600 to in the buff. Buff-colored uniforms of New York City volunteer firefighters since 1820s led to meaning "enthusiast" (1903).
The Buffs are men and boys whose love of fires, fire-fighting and firemen is a predominant characteristic. [N.Y. "Sun," Feb. 4, 1903]
"well-built, hunky," 1980s, from buff (v.) "polish, make attractive."
"to polish, make attractive," 1885, in reference to the treatment of buff leather or else to the use of buff cloth in polishing metals, from buff (n.). Related: Buffed; buffing.
[originally fire buff, because New York City volunteer firefighters about 1820 wore buff-colored, light brownish yellow coats; transferred to persons who like to watch fires, then to enthusiasts in general]
[1604+; probably fr the pale yellowish color of the leather called buff, likened to skin]
(also buffed, buffed out) Well-built; muscular; hunky: Looking mighty buff, by the way (1980s+ Teenagers)verb
(also buff out) To do body-building; put on muscle; become brawnier: Fudgie wondered if Tweezer had buffed out in San Quentin (1980s+ Teenagers)verb phrase
(also buff up) To be ingratiating and attentive, so as to keep on good terms: Gotta go. Gotta buff (1990s+ Hollywood)
[probably fr buff, ''polish, make attractive,'' a process originally done with a leather buff stick; the adj sense may be derived fr buffalo, as an image of strength]
To make a patient's chart look good, esp in preparing him or her for discharge
[1970s+ Medical; fr buff, ''to polish'']
An HH53 long-range rescue helicopter, called a ''big ugly fat fellow'' (1960s+ Air Force)