A yoke or team (i.e. Pair); hence, an acre (i.e. Day's task for a yoke of cattle to plough) -- acre, couple, X together, two (donkeys), yoke (of oxen).
צֶ֫מֶד noun masculine1 Kings 19:19 couple, pair; — ׳צ construct Judges 19:3 +; suffix צִמְדּוֺ Jeremiah 51:23; plural צְמָדִים 1 Kings 19:19; 2 Kings 9:25 (but see below); construct צִמְדֵּי Isaiah 5:10 (Ges§ 93m); —
1 couple, pair, usually of animals, ׳צ חֲמֹרִים Judges 19:3, 10; 2 Samuel 16:1; בָּקָר (הַ) ׳צ span of oxen 1 Samuel 11:7; 1 Kings 19:21, plural of more than one span 19:19 (ploughing), Job 1:3; 42:12; מְּרָדִים צֶמֶד 2 Kings 5:17; ׳צ מָּרָשִׁים Isaiah 21:7, 9 a pair of horsemen; plural also of one pair of riders 2 Kings 9:25 (but read probably צֶמֶד, so Kit); ׳צ alone = span (of oxen) Jeremiah 51:23.
2 a measure of land (only square measure in OT) like acre; originally apparently what a span can plough (in a day; see NowArchaeology i. 202 BenzArchaeology 208; compare modern faddan, = what, can be ploughed in a season SchumacherZPV xii (1889), 163 f., Across Jordan 22, or in a day BergheimPEQ, 1894, 192, Ency. Bib.ACRE), ׳צ שָׂדֶה 1 Samuel 14:14 (on text see Dr HPS); צִמְדֵּיכֶֿרֶם Isaiah 5:10.