demijohn
Concise Oxford English Dictionary © 2008 Oxford University Press:
demijohn/ˈdemiʤɒn/
▶noun a bulbous narrow-necked bottle holding from 3 to 10 gallons of liquid.
– origin C18: prob. an alt. of Fr. dame-jeanne ‘Lady Jane’, assoc. with demi- and the given name John.
'demijohn' also found in these Oxford entries:

