English and Dutch, from the Hebrew forename Yaakov/Yakov; OT Genesis 25 et seq.

The meaning is taken to be "heel grabber" because Jacob was reputed to have clutched the heel of his twin brother Esau when emerging from Rebecca's womb [OT Genesis 25:26].  Chambers extends the meaning to include: "follower", "supplanter" or "deceiver", all of which can be derived from the biblical story.

Of the pet names, Jaap, Cobus and Coos are Dutch and Jake is English; Jep is Danish, from Jakob; Ib is a derivative via Jep; Kuba is Polish and Koppel is Yiddish.

Jacob occurs very rarely in the 1841 Census of Aberdeenshire whereas Jacobina, the Scottish feminine form, is slightly more frequent.

In old documents in Latin, Iacobus/Jacobus or Iacomus/Jacomus was used, with appropriate case endings, for James or Jacob and the latter two names have been used synonymously ever since.

A correspondent [LA] has pointed out that many [?most] earlier manuscripts used a common script for capitals "I" & "J". Thus Jacob may have been written and then transcribed as Iacob. Many on-line services have transcribed original documents faithfully so this version might be the one to look for in the indexes to earlier records.