E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
To marry. Very strangely, splice means to split or divide. The way it came to signify unite is this: Ropes ends are first untwisted before the strands are interwoven. Joining two ropes together by interweaving their strands is splicing them. Splicing wood is joining two boards together, the term being borrowed from the sailor. (German, spleissen, to split.)