Ok, so what’s the deal with swash-buckling? What is a swash, and how does one buckle it?
*swashbuckler - 1560, from swash “fall of a blow” (see swash) + buckler “shield.” The original sense seems to have been “one who makes menacing noises by striking his or an opponent’s shield.” Swashbuckling (adj.) is late 17c. *
http://www.geocities.com/etymonline/s15etym.htm
- Tamerlane
If there is any definite etymology to this phrase, one swashes one’s buckler (a small shield). Swashing is basically banging or striking: a swashbuckler will do a lot of noisemaking with his shield and sword to avoid actually fighting (OK, the meaning has changed a little).