I supose most people have lost interest in this by now... :-)
but pedants just won't give up... :-0

Note the alleged dates for first usage...

From:
Merriam Webster on line
http://www.m-w.com/

Main Entry: vi·bra·to
Pronunciation: vi-'brä-(")tO, vI-
Function: noun
Inflected Form(s): plural -tos
Etymology: Italian, from past participle of vibrare to vibrate, from Latin
Date: circa 1876
: a slightly tremulous effect imparted to vocal or instrumental tone for added warmth and expressiveness by slight and rapid variations in pitch

Main Entry: trem·o·lo
Pronunciation: 'tre-m&-"lO
Function: noun
Inflected Form(s): plural -los
Etymology: Italian, from tremolo tremulous, from Latin tremulus
Date: circa 1801
1 a : the rapid reiteration of a musical tone or of alternating tones to produce a tremulous effect b : vocal vibrato especially when prominent or excessive
2 : a mechanical device in an organ for causing a tremulous effect