Lojban has taken the word "monsuta" from Toki Pona
http://jbovlaste.lojban.org/dict/monsuta?bg=1;langidarg=2
and one of the possible etymons of the Toki Pona word 'lupa' is the Lojban word "clupa"
Lojban is known for being hard to speak
https://groups.google.com/forum/#!topic/lojban/e7cg5vy2EfA
but less difficult then Ikhtuil, ofcourse
Another possible etymology for the Toki Pona word "lupa" is the Croatian word "rupa" 'hole'
Concerning Lojban, I'm having troubles with "gismu", "brivla" and "rafsi" word classes...
That learning curve to get access to the meaning of these concepts is quite steep for an already skeptical person...
I"ve found this Toki Pona - Lojban word list:
https://jbotcan.org/tokipona/
and
Toki Pona enhanced (TPE) "employing advances in the science of Lojban"
@jansegers Great to have another #conlang enthusiast here! I'm a Lojbanist myself :)