building string from big list of words

I don't know the type of this algmaybe it's famous..

I have a liste of this forme L = [ ["a"] , ["b"] , ["c"] ] , [ ["d"] , ["e"] , ["f"] ] , ["g"], ["h"], ["i"] ] ,[ ["j"] , ["k"] , ["l"] ]

where the letter are words and the length of L could be from 2 to 50 elements but inside the list are always 3 elements longue.

And i want to create a list who build all this string :

"adgj" "adgk" "adgl" "adhj" "adhk" "adhl" "adij" "adik" "adil" "aegj" ect all the way to "cfil"

could someone tell me what to do or where to look for?

Thank's a lot for your help..