What does 'what' mean? (What with being so busy both at work and and at...)

English as a Second Language English Vocabulary, Grammar and Idioms
1

what is the significance of " what" in that context?
“What with being so busy both at work and and at home,she became increasingly tired and bad-tempered.”

2

.
what with

  1. (idiomatic) Owing to; because of; as a result of.

She was sleeping very badly these days, what with the new baby and all the activity surrounding him. (Wikipedia)
.