What is the meaning of -jo?

Forms gender-neutral affectionate derivatives of names.

Wennergren, Bertilo (2019) “J° kaj PJ°”, in Plena Manlibro de Esperanta Gramatiko (in Esperanto), retrieved 2019-04-06

postpositive form of je

forms causative verbs from transitive verbs, intransitive verbs with agent-like arguments, and a handful of intransitive verbs with patient-like arguments that begin with e-; intransitive verbs converted this way remain morphologically intransitive

Source: wiktionary.org