hall·mark / ˈhôlˌmärk/ • n. a mark stamped on articles of gold, silver, or platinum in Britain, certifying their standard of purity. ∎  a distinctive feature, esp. one of excellence: the tiny bubbles are the hallmark of fine champagnes.• v. [tr.] stamp with a hallmark. ∎  designate as distinctive, esp. for excellence.

hallmark a mark stamped on articles of gold, silver, or platinum by the British assay offices, certifying their standard of purity. Recorded from the early 18th century, the word refers to Goldsmiths' Hall in London, where articles were tested and stamped with such a mark.
don't halloo till you are out of the wood you should not exult until danger and difficulty are past (halloo means shout in order to attract attention). The saying is recorded from the late 18th century.

hallmark Official stamp used by British government assay offices to mark the standard of gold and silver articles. The mark has four elements: the standard mark, showing the purity of the metal; the office mark, bearing the assay office's cipher; the date mark; and the maker's mark.