From a root of uncertain signification; a tamarisk tree; by extension, a grove of any kind -- grove, tree.
Englishman's Concordance
1) tamarisk tree Part of Speech: noun masculine A Related Word by BDB/Strong’s Number: from a root of uncertain signification Same Word by TWOT Number: 179a
Brown-Driver-Briggs
אֵ֫שֶׁלnoun masculinetamarisk-tree (Arabic , Sabean אתֿל SabDenkm65 compare DHMBS ii. 958; on an Aramaic אַתְלָא see LöwNo. 38; compare TristrFFP 250) planted by Abraham Genesis 21:33 (J); in 1 Samuel 22:6 Saul is dwelling בַּגִּבְעָה תַּחַתהָֿאֵשֶׁל בָּרָמָה; 1 Samuel 31:13 Saul and his sons are buried ׳תַּחַתהָֿא; it was perhaps a sacred tree, marking shrine.
Genesis 21:33 HEB: וַיִּטַּ֥ע אֶ֖שֶׁל בִּבְאֵ֣ר שָׁ֑בַע NAS: [Abraham] planted a tamarisk tree at Beersheba, KJV: And [Abraham] planted a grove in Beersheba, INT: planted A tamarisk Beersheba called
1 Samuel 22:6 HEB:בַּגִּבְעָ֜ה תַּֽחַת־ הָאֶ֤שֶׁל בָּֽרָמָה֙ וַחֲנִית֣וֹ NAS: under the tamarisk tree on the height KJV: in Gibeah under a tree in Ramah, INT: Gibeah under the tamarisk the height his spear
1 Samuel 31:13 HEB:וַיִּקְבְּר֥וּ תַֽחַת־ הָאֶ֖שֶׁל בְּיָבֵ֑שָׁה וַיָּצֻ֖מוּ NAS: them under the tamarisk tree at Jabesh, KJV: and buried [them] under a tree at Jabesh, INT: and buried under the tamarisk Jabesh and fasted