英语词源字典 - 在线词源网站

J [J 词源字典]: the letter is a late modification of Roman -i-, originally a scribal creation in continental Medieval Latin to distinguish small -i- in cursive writing from the strokes of other letters, especially in the final positions of words. But in English, -y- was used for this, and -j- was introduced into English c. 1600-1640 to take up the consonantal sound that had evolved from -i- since Late Latin times. This usage first was attested in Spanish, where it was in place before 1600. English dictionaries continued to lump together words beginning in -i- and -j- until 19c., and -j- formerly was skipped when letters were used to express serial order.

Used in modern writing to represent Latin -i- before -a-, -e-, -o-, -u- in the same syllable, which in Latin was sounded as the consonant in Modern English you, yam, etc., but the custom is controversial among Latinists:
The character J, j, which represents the letter sound in some school-books, is an invention of the seventeenth century, and is not found in MSS., nor in the best texts of the Latin authors. [Lewis]
In words from Hebrew, -j- represents yodh, which was equivalent to English consonantal y (as in hallelujah) but in many names it later was conformed in sound to the -j- of Latin or French (Jesus).[J etymology, J origin, 英语词源]
skip (v.): c. 1300, "to spring lightly," also "to jump over," probably from a Scandinavian source such as Old Norse skopa "to take a run," Middle Swedish skuppa "to skip, leap," from Proto-Germanic *skupan (cognates: Middle Swedish skuppa, dialectal Swedish skopa "to skip, leap"). Related: Skipped; skipping.

Meaning "omit intervening parts" first recorded late 14c. Meaning "fail to attend" is from 1905. Meaning "to cause to skip or bound" is from 1680s. The custom of skipping rope has been traced to 17c.; it was commonly done by boys as well as girls until late 19c.