Handkerchiefs is correct.
Get Out Your Handkerchiefs was created on 1978-01-11.
Cylinders.
McDonald's
cobwebs
Martinez's
boats
The plural is handkerchiefs. All you have to do to make "handkerchief" plural is add an "s".
Handkerchiefs is the plural. The singular form of the word is handkerchief.
You wouldn't pluralize "processing", but you would pluralize "process" making more than one process "processes".
Fournesses is the plural of Fourness
Sirs is the plural of sir
Folisis is the plural of Folisi