i seen this thread last night, and i ended up wracking my brains for where i knew the name 'jukola.mdl' from. i even went to sleep with the damn words going over and over in my head. i know i've had it crop up before, and for some reason, the fish pond entity (func_fish_pool apparently) kept looming in my thoughts. i found a few sites that seemed to support a connection with that entity, but they were in german, so i'm very sketchy about the full content.
i found some other sites that had it connected with other entities, like your func_button, and i'm left feeling that it may be a generic name, given to any entity, including brush based, that calls for the engine to load something that doesn't exist.
i'm probably way off with this though.

and it's still bugging me where i know the name from.