A primitive root; to fold together; figuratively, to repeat -- double.
Englishman's Concordance
1) to double, fold double, double over 1a) (Qal) to double over 1b) (Niphal) to be doubled Part of Speech: verb A Related Word by BDB/Strong’s Number: a primitive root Same Word by TWOT Number: 1019
Brown-Driver-Briggs
כָּפַלverbdouble, double over (late) (Late Hebrew id.; Aramaic כְּפַל; ᵑ7. כִּיפְלָא, כּוּפְלָה, Nabataean כפל EutNab. No. 20, 7the double; Christian-Palestinian Aramaic SchwIdioticon 46; North Syriac id.; Arabic the double, posteriors, buttocks; Ethiopic is divide, a part) —
QalPerfect2masculine singular וְכָפַלְתָּ֫Exodus 26:9and thou shalt double over the sixth curtain, i.e. probably use it double (Di); Passive participleכָּפוּלfolded double, of the breastpiece (חשֶׁןׅExodus 28:16; Exodus 39:9 (twice in verse).
Niph`alImperfect3feminine singular וְתִכָּפֵלEzekiel 21:19and let the sword be doubled, but very dubious; Co reads plausibly תְּשַׁכֵּלlet the sword bereave (compare VB).
Exodus 26:9 HEB:הַיְרִיעֹ֖ת לְבָ֑ד וְכָפַלְתָּ֙ אֶת־ הַיְרִיעָ֣ה NAS: by themselves, and you shall double over the sixth KJV: curtains by themselves, and shalt double the sixth INT: curtains themselves shall double curtain the sixth
Exodus 28:16 HEB:רָב֥וּעַ יִֽהְיֶ֖ה כָּפ֑וּל זֶ֥רֶת אָרְכּ֖וֹ NAS: It shall be square [and] folded double, a span KJV: Foursquare it shall be [being] doubled; a span INT: shall be square become folded A span length
Exodus 39:9 HEB:רָב֧וּעַ הָיָ֛ה כָּפ֖וּל עָשׂ֣וּ אֶת־ NAS: the breastpiece folded double, KJV: the breastplate double: a span INT: square become folded made the breastpiece
Exodus 39:9 HEB:וְזֶ֥רֶת רָחְבּ֖וֹ כָּפֽוּל׃ NAS: folded double, a span KJV: the breadth thereof, [being] doubled. INT: span wide double
Ezekiel 21:14 HEB:אֶל־ כָּ֑ף וְתִכָּפֵ֞ל חֶ֤רֶב שְׁלִישִׁ֙תָה֙ NAS: and let the sword be doubled the third time, KJV: and let the sword be doubled the third INT: about hands be doubled the sword the third