Wikipedia: Half-mast (British, Canadian and Australian English) or half-staff (American English) refers to a flag flying below the summit of a ship mast, a pole on land, or a pole on a building. In many countries this is seen as a symbol of respect, mourning, distress, or, in some cases, a salute. Most English-speaking countries use the term half-mast in all instances. In the United States, this refers officially only to flags flown on ships, with half-staff used on land.
And not to feed a stuffed puppy–
1708 London Gazette: “The Ships Flags, which were only half-staff high.”
and . . .
1627 Captain Smith Seaman’s Grammar: “Hoise your Sailes half mast high.”
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Correct term would be: half staff
Masts are on ships.
Wikipedia: Half-mast (British, Canadian and Australian English) or half-staff (American English) refers to a flag flying below the summit of a ship mast, a pole on land, or a pole on a building. In many countries this is seen as a symbol of respect, mourning, distress, or, in some cases, a salute. Most English-speaking countries use the term half-mast in all instances. In the United States, this refers officially only to flags flown on ships, with half-staff used on land.
And not to feed a stuffed puppy–
1708 London Gazette: “The Ships Flags, which were only half-staff high.”
and . . .
1627 Captain Smith Seaman’s Grammar: “Hoise your Sailes half mast high.”
OED 1971
Shimmer me timbers! Ahoy mates!