marlinspike (n.)

"pointed iron tool used by sailors to separate strands of rope," 1620s, from spike (n.) + marlin, Middle English merlin (early 15c.) "small line of two strands, used for seizings," from Middle Dutch marlijn "small cord," from marlen "to fasten or secure (a sail)," which is probably frequentative of Middle Dutch maren "to tie, moor" (see moor (v.)). Influenced in Dutch by lijn "line" (n.).