The Dutch word for "lent" is vasten (similar to the German word), but the Dutch word for "spring" is lente. In other words, the English word "lent" originally just meant spring, and in fact is related to "long" and "lengthen"--it's the season when the days are gettig longer. The early Anglo-Saxons were incorrigibly Northern Hemisphere-biassed.
There's no connection with English "lent" and Latin lente--lent just seems to go slowly.
Why did every movement toward total decadence in the world seem to start in the sixties? Vatican II was no more enlightening than the Great Society and improbably more harmful.