because
I couldn't attend the meeting because, because of the storm, the roads were closed.
The construction is grammatically valid: the comma clarifies the distinct roles of each 'because' — one as a conjunction for the main clause and the other within a prepositional phrase.
Meanings
for the reason that; introducing an explanation of cause or motive
- We left early because of the storm.
- She studied music because she loved performing.
the same word in informal speech, often heard as 'becuz' or 'cuz'
- I'm tired 'cause it's late.
- He said 'just because' when asked why.
Word origin
From Middle English bi cause ('by reason of, on account of'), originally a two-word phrase that fused. 'By cause' itself was a calque of Old French par cause de. The full sense crystallized in late Middle English as a single word and became the most basic explanatory connector in English.
Fun fact
Internet usage in the 2010s gave 'because' a new grammatical role — used as a preposition with a noun, as in 'I'm staying home because rain' or 'Because science.' This 'because + noun' construction, originally a joke pattern, has been admitted into descriptive dictionaries as a legitimate informal usage.