Origin of telltale
- an outward indication of something concealed
- (as modifier)a telltale paw mark
- another word for dogvane
- one of a pair of light vanes mounted on the main shrouds of a sailing boat to indicate the apparent direction of the wind
Divulge secrets, as in Don't trust him; he's apt to tell tales. This expression was first recorded about 1350. A variant, tell tales out of school, first recorded in 1530, presumably alluded to schoolchildren gossiping but was soon broadened to revealing secret or private information. Both may be obsolescent.