Don't look a gift horse in the mouth Don't be ungrateful when
you receive a gift. Proverbs are 'short and expressive sayings,
in common use, which are recognized as conveying some accepted
truth or useful advice'. This example, also often expressed as
'never look a gift horse in the mouth', is as pertinent today as
it ever was. As horses develop they grow more teeth and their
existing teeth begin to change shape and project further
forward. Determining a horse's age from its teeth is a
specialist task, but it can be done. This incidentally is also
the source of another teeth/age related phrase - long in the
tooth. The advice given in the 'don't look...' proverb is: when
receiving a gift be grateful for what it is; don't imply you
wished for more by assessing its value. As with most proverbs
the origin is ancient and unknown. We have some clues with this
one however. The phrase appears in print in English in 1546, as
"don't look a given horse in the mouth", in John Heywood's A
dialogue conteinyng the nomber in