conc▪ In ClassAr lexicography, ǧadwal is generally treated s.r. ↗√ǦDL the basic meaning of which is ‘to twist tight, braid, plait’ (↗ǧadala).
▪ The relation between the two values, ‘twisting’ and ‘rivulet’, is not immediately evident, but if ǧadwal should indeed be dependent on ǧadala one could perh. explain it as *‘trickles uniting (“intertwining”) and thus forming a rivulet’. Interestingly enough, ǧadwal ‘rivulet’ is the very earliest lexeme that a search for first attestations of items from √ǦDL yields in DHDA.
▪ The use of ǧadwal [v1] ‘rivulet’ in the sense of [v2] ‘ruled line; column; list, roster; chart, table, schedule’ – the most prevalent value in MSA – can perh. support the above explanation ‘rivulet < twisting, intertwining’ as also a ‘table, chart, roster’ may be regarded as an assembly of *‘intertwining’ lines, the result of some “twisting”. Ar lexicographers, as summarized in Lane ii 1865, describe ǧadwal, var. ǧidwal, as »rivulet, streamlet (whether natural, or formed artificially for irrigation; being often applied to a streamlet for irrigation, in the form of a trench, or gutter]; (hence:) [expr.] ĭstaqāma ǧadwaluhum, their affair, or case, was, or became, in a right, a regular, or an orderly, state’, like the ǧadwal when its flow is uniform and uninterrupted; [expr.] ĭstaqāma ǧadwal al-ḥāǧǧ, the caravan of the pilgrins formed an uninterrupted line; (hence also:) kind of small vein; (and:) ǧadwal kitāb, ruled line (such as is ruled round a page, &c.); column, table (of a book)«.
▪ Morphologically, ǧadwal could be described as a (dimin.?) FaʕwaL~FiʕwaL formation (though no such pattern has been identified by grammarians so far…).