Meaning: mutual sorrow, shared mourning.
Usefulness: 1 (Can be used seriously: "the nation's collugency at this sad time..." or not: "The outer suburbs of Melbourne were cast into collugency at Collingwood's elimination from the finals.")
Logofascination: 1 (I am reasonably sure that Sir Thomas invented this one, albeit by Anglicising the Latin collugere.)
In the wild: No.
Which is used in: G&P, La Tiers-Livre, XLVIII: How Gargantua showeth that the children ought not to marry without the special knowledge and advice of their fathers and mothers. Gargantua doesn't show this, so much as talk about the pain suffered by parents when their daughters marry without consent. He's quiet on the subject of sons, despite speaking to his son at the time.
Neither would I have you to believe that the discomfort and anxiety of the Lacedaemonians, when the Greek Helen, by the perfidiousness of the adulterous Trojan, Paris, was privily stolen away out of their country, was greater or more pitiful than this ruthful and deplorable collugency of theirs?Ruthful being the opposite of ruthless, of course, and probably more like rueful in this context.