What’s the origin of the exclamation, “Strewth!”? I have a feeling it comes from “God’s truth!”, but that’s only a guess.
Not the very best source, but…
I have an annotated edition of “Monty Python’s Flying Circus” scripts, and the annotation to “strewth” indeed says it’s a corruption of “God’s truth.”
Thanks. I was watching Battle of Britain last night, and one of the pilot’s exclaimed “God’s truth!” It sounded like “God, strewth!” (and I remembered that “Zounds!” was from “God’s wounds!”) so I thought I’d ask for the Straight Dope. 
The “God’s truth” is the explanation I’ve heard. I probably got it from the Word Detective, a very interesting sight in its own right. IIRC, other words coming from “God’s wounds” are “Gadzooks!” and “Wow”.
“God’s wounds” --> “zounds”
“God’s hooks” (hands) --> “Gadzooks”
Exactly as others have posted.
OED cites first used by Kipling, 1892.