The great Swedish sinologist Bernhard Karlgren, in his very instructive little 1923 handbook Sound and Symbol in Chinese (p. 30 in my first edition), tells us that:
Just as a Swede at once distinguishes by the melody gìftet (the marriage) from gíftet (the poison), the Chinese distinguishes his words by their tones.So now I am speculating idly on this Scandinavian connection between marriage and poison. This is the region that produced August Strindberg, right? And Henrik Ibsen? Hmmm.
(Do people still remember Dr. Crippen? The peelers have written him up here.)