blow received by a bystander; getting dragged into someone else's fight
Used in the idiom 側杖を食う (そばづえをくう), meaning to suffer harm or get involved in trouble not originally one's own. Often refers to being caught in the crossfire of a dispute or conflict.
Caught in the crossfire of the couple's quarrel, the child started crying.
In company factional disputes, uninvolved employees sometimes get dragged in.
Common spelling using the kana そば for clarity.
Kanji spelling; 側 can also be read がわ or そく, so the reading may not be immediately obvious.
Rare variant using 傍.
Compound of そば (side, nearby) and 杖 (stick, cane). The image is of a blow from a cane meant for someone else hitting a bystander, extended metaphorically to any collateral damage.