black mail vs white mail
The word is variously derived from the word for tribute (in modern terms, protection racket) paid by English and Scottish border dwellers to Border Reivers in return for immunity from raids and other harassment. The "mail" part of blackmail derives from Middle English male, "rent, tribute." This tribute was paid in goods or labour (reditus nigri, or "blackmail"); the opposite is blanche firmes or reditus albi, or "white rent" (denoting payment by silver). Alternatively, Mckay derives it from two Scottish Gaelic words blathaich pronounced (the th silent) bla-ich (to protect) and mal (tribute, payment). He notes that the practice was common in the Highlands of Scotland as well as the Borders.
