What is "to swear off"

Swear \Swear\, v. i. [imp. Swore, formerly Sware; p. p. Sworn; p. pr. & vb. n. Swearing.] [OE. swerien, AS. swerian; akin to D. zweren, OS. swerian, OHG. swerien, G. schw["o]ren, Icel. sverja, Sw. sv["a]rja, Dan. sv[ae]rge, Icel. & Sw. svara to answer, Dan. svare, Dan. & Sw. svar an answer, Goth. swaran to swear, and perhaps to E. swarm.

1. To affirm or utter a solemn declaration, with an appeal to God for the truth of what is affirmed; to make a promise, threat, or resolve on oath; also, to affirm solemnly by some sacred object, or one regarded as sacred, as the Bible, the Koran, etc.

   Ye shall swear by my name falsely.
   --Lev. xix. 1

2. I swear by all the Roman gods.
   --Shak.

   2. (Law) To give evidence on oath; as, to swear to the truth of a statement; he swore against the prisoner.

3. To make an appeal to God in an irreverant manner; to use the name of God or sacred things profanely; to call upon God in imprecation; to curse.

   [I] swore little; diced not above seven times a week.
   --Shak.

   To swear by, to place great confidence in a person or thing; to trust implicitly as an authority. ``I simply meant to ask if you are one of those who swear by Lord Verulam.''
   --Miss Edgeworth.

   To swear off, to make a solemn vow, or a serious resolution, to abstain from something; as, to swear off smoking. [Slang]