From Old Swedish þænni, from Old Norse þessi, sjá, (runic: ᛋᛅᛋᛁ = sāsi), from the demonstrative pronoun sá + an intensive suffix -si. The form denna is specifically from the Old Norse masculine accusative form þenna.
- this, that (depending on context).
Dessa skrifter är heliga!
- These writings are sacred.
Varför detta ständiga gräl?
- Why this neverending fighting?
The standard has been that denna or its inflected forms are followed by a noun in the indefinite forms but in certain dialects such as parts of Scania it's common to have a noun in the definite form, such as what you do with den där and den här.
- this one, this (if not followed by a noun, in neuter), that one, that (if not followed by a noun, in neuter) (depending on context).
Vad är detta?
- What is this?
Jag vill ha denna!
- I want this one!
- Alternative form of