MAIN (from the Aryan root which appears in " may " and " might," and Lat. magnus, great), a word meaning properly power or strength, especially physical. This use chiefly survives in the expression " with might and main." The word is more common as a substantival elliptical use of the adjective, which usually has the sense of principal or chief in size, strength, importance, etc. Thus " the main," the high open sea, is for " main sea," cf. " mainland," the principal part of a territory excluding islands and sometimes far-projecting peninsulas. The expression " the Spanish main " properly meant that part of the main land of the N.E. coast of South America stretching from the Orinoco to the Isthmus of Panama, and the former Spanish possessions in Central America bordering on the Caribbean Sea, but it is often loosely used, especially in connexion with the buccaneers, of the Caribbean Sea itself. The term " main " is also thus used of a principal pipe or cable for conducting gas, water, electricity, etc. The elliptical use does not appear, however, in such expressions as main road, line, stream. Another use of the .word " main " has a somewhat obscure history. It appears as a term in the game of hazard, and also in cock-fighting. In the last it is used for a match, and for the cocks engaged in a match. In hazard it is the number called by the " caster " before the dice are thrown; this may be any number from five to nine inclusive. The usual derivation is from the French main, a hand, but according to the New English Dictionary there is no evidence for this, and the more probable explanation is that it is an adaptation of " main " meaning principal or chief. From this use of the word in hazard the expression " main chance " is derived. " Main," a shortened form of domain or demesne, only now survives in Scotland, usually in the plural " mains " for a home farm.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)