The last post [oops, one intervened] revealed that native English one, the cognate of Spanish uno, is hiding in plain sight in the word alone, which coalesced from the phrase all one, as well as in the subsequent alone, lone, and lonely. The combining of all one into alone took place before one came to be pronounced the way it is now, so the -one in alone and lone and lonely preserves its earlier pronunciation, which was the same as the unrelated own. Another place where the older pronunciation of one helps it to hide in plain sight is in only, which came into existence as one-ly. As a result, the familiar phrase only one is etymologically and redundantly equivalent to one-ly one.
Latin had earlier created its own version of one-ly: it took un-, the root of unus, the ancestor of Spanish uno, and added a suffix to create the adjective unicus, whose meanings were ‘only, one and no more, sole, single, alone of its kind.’ Spanish acquired that as único, and Old French as unique, which then passed into English. The sense of unique is ‘one of a kind,’ but increasingly many English speakers have lost sight of that and have started saying very unique, which amounts to ‘very one of a kind.’ Even worse is more unique, which amounts to ‘more one of a kind.’ Either something is one of a kind or it isn’t; there’s no such thing as *three-fourths of a kind.
If English added its adverb-forming suffix to one to create only, it’s only to be expected that Spanish would have done likewise: from único came the únicamente that means ‘only.’
© 2011 Steven Schwartzman