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 6 April 2019

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

romanization of -𐌾𐍉

Source: wiktionary.org