The phrase "rule of thumb" is used in some sources to refer to a husband's right under old common law to chastise his wife.
The origins of this phrase and how it came to be related to domestic abuse are discussed in: Henry Ansgar Kelly, "Rule of Thumb and the Folklaw of the Husband's Stick" in 44 Journal of Legal Education, 341-65.
See also:
Donna M. Nesselbush, "From Rule of Thumb to Rule of Law: The Evolution of the Rhode Island Legal System's Response to Domestic Abuse" in 25 Suffolk Law Review, 421-59.
Cheryl A. Wilkerson, "Spouse Abuse: Proposal for a New Rule of Thumb" in 17 University of Richmond Law Review, 633-60.
Henry Ansgar Kelly, "Rule of Thumb and the Folklaw of the Husband's Stick" in 44 Journal of Legal Education, 341-65 - available via HeinOnline
Donna M. Nesselbush, "From Rule of Thumb to Rule of Law: The Evolution of the Rhode Island Legal System's Response to Domestic Abuse" in 25 Suffolk Law Review, 421-59 - available via HeinOnline
Cheryl A. Wilkerson, "Spouse Abuse: Proposal for a New Rule of Thumb" in 17 University of Richmond Law Review, 633-60 - available via HeinOnline