Ducky notices something the sequel animators didnt "You are a Spiketail, so we will call you 'Spike'."
The subject(s) detailed in this article has/have been given a conjectural (and, as a result, unofficial) name, due to the lack of an official name for the article subject(s) to be referred to by.
"Onehorn" is a fan-derived term for one-horned ceratopsians. This term comes from the single, large nose-horn that these species possess.