The german noun Weile is cognate to while and means "while"[Noun], "spell"[period of time] "duration", "span of time". Adding the suffix -ig is a way to create an adjective from a noun.
The verb weilen means "to rest", "to stay at one place (for a while)".
Hence, the suffix -weilig means as much as "during", "while"[Adjective], "in the time of". But it is not always possible to guess the meaning, since it has changed over time or has focussed on a particular idea which is only loosely related to the notion of Weile:
- langweilig literally translates to something like "long-during, long lasting". It came to mean "boring" as figurative speech.
- kurzweilig, the opposite to langweilig, "diverting", "amusing"
- derweilig, more common now as derweilen: "in the meantime"
- jeweilig, more common now as jeweils: "each", "at a time"
- zeitweilig: literally translates to "during a certain time", meaning "temporary", "intermittant",
- einstweilig: literally translates to "once-whiley", "at a certain time", is used primarily in the legal term einstweilige Verfügung: "injunction" and means "provisional", "interlocutory".
However, as Schmuddi points out in a comment, all examples containing -weilig are lexicalized words with opaque, non-compositional meaning and -weilig is not a productive morpheme of German anymore, you could not use it to form a new word anymore.
