The phrase, 'mull over' came from the process by which apple cider is made. The mulling was the cooking of the liquid from the apples after adding spices. This sometimes took several hours to complete.
'Mull Set' . I think you mean 'NULL SET'. This means a set with no elements, or an empty set.
"He stayed in alone that evening to mull things over" "As it's Christmas, let's mull some wine" It's literally meaning is to "heat up" ; metaphorically it has come to mean "think" or "deeply consider"
"Mull" is a verb.
Martin Mull's birth name is Martin Eugene Mull.
Brandon Mull's parents' names are David and Emily Mull.
What's a Mull? Plum
Carter Mull was born in 1977.
Clay Mull was born in 1979.
Jack Mull was born in 1943.
Mull Kireedom was created in 1968.
Gary Mull was born in 1937.