Maendeleo development is an interesting word. Ma -ende- leo the 'goings' today
Am I right here?
I think it actually comes from the verb kuendelea, which means "to continue". I believe it does ultimately come from kuenda, but I'm not quite sure what the -le derivational suffix means.
it does indeed. the -ele- infix is prepositional. It transforms "to go" into "to go on" (or as you say, "to continue/develop").
There are a few different forms of the prepositional infix: kusoma = to read, kusomea = to read to kupika = to cook, kupikia = to cook for kufungua = to open, kufungulia = for opening
The prepositional form uses an "e" if the preceding vowel is an e or o (like in kuEnda and kusOma) and an "i" if the preceding vowel as an a, i or u. The added "l" is used when the second to last letter of the verb is also a vowel (I think that kuendelea is actually the prepositional form of kuendea, which is an unused prepositional form of kuenda).