warder
Concise Oxford English Dictionary © 2008 Oxford University Press:
warder/ˈwɔːdə(r)/
▶noun (fem. wardress) chiefly Brit. a prison guard.
– origin ME (denoting a watchman or sentinel): from Anglo-Norman Fr. wardere, from Old North. Fr. warder ‘to guard’.
'warder' also found in these Oxford entries:

