from The Century Dictionary.
- noun A tax paid in ancient times by merchants, etc., for leave to expose or display their goods for sale in markets.
Sorry, no etymologies found.
I have a Jesuit friend (also a medievalist) that occasionally has people over to his church for an "ostensio reliquarum": a showing of relics.
There were also sermons in English (see next chapter); Jocelin de Brakelonde says in his chronicle that sermons were delivered in churches, "gallice vel potius anglice, ut morum fieret edificatio, non literaturæ ostensio," year 1200
_Quidquid ostendit peccatum, iram seu mortem, id exercet officium legis; lex et ostensio peccati seu revelatio irae sunt termini convertibiles_. "