الإبط: ما تحت الجناح، يذكر ويؤنث، والجمع آباط.
The armpit: what is beneath the wing, it is masculine and feminine, and the plural is 'ābāṭ'.
وحكى الفراء عن بعض الأعراب: فرفع السوط حتى برقت إبطه.
And al-Farra' narrated from some of the Bedouins: He raised the whip until his armpit flashed.
وتأبط الشئ، أي جعله تحت إبطه.
And he 'ta'abbaṭa' the thing, meaning he placed it under his armpit.
والتأبط: الاضطباع، وهو أن يدخل رداءه تحت يده اليمنى ثم يلقيه على عاتقه الأيسر.
And 'al-ta'abbuṭ': is 'al-iḍṭibāʿ', which is to tuck one's cloak under the right hand then throw it over the left shoulder.
وكان أبو هريرة رضي الله عنه رديته التأبط.
And Abu Hurayrah, may God be pleased with him, his riding companion was 'al-Ta'abbut'.
والإبط من الرمل: منقطع معظمه.
And the 'ibṭ' of a sand dune: its lower, larger part.
واستأبط فلان، إذا حفر حفرة ضيق رأسها ووسع أسفلها.
And so-and-so 'ista'baṭa', if he dug a pit whose head was narrow and its base was wide.
يحفر ناموسا له مستأبطا
Digging a hiding place for himself, a 'musta'biṭan'.
وكان ثابت بن جابر الفهمي يسمى تأبط شرا، لانهم زعموا أنه كان لا يفارقه السيف.
And Thābit ibn Jābir al-Fahmī was called Ta'abbat Sharran, because they claimed the sword never left him.
تقول: جاءني تأبط شرا، ومررت بتأبط شرا، تدعه على لفظه، لانك لم تنقله من فعل إلى اسم، وإنما سميت بالفعل مع الفاعل جميعا رجلا، فوجب أن تحكيه ولا تغيره.
You say: 'Jā'anī Ta'abbat Sharran' (Ta'abbat Sharran came to me), and 'Marartu bi-Ta'abbat Sharran' (I passed by Ta'abbat Sharran), you leave it in its original form, because you have not transferred it from a verb to a noun; rather, a man was named by the verb and the doer together, so it is obligatory to report it as is and not change it.
وكذلك كل جملة يسمى بها، مثل برق نحره، وذرى حبا.
And likewise every phrase by which a name is given, such as 'Bariqa Naḥruhu' (His throat flashed) and 'Dharā Ḥubbā' (He piled up love).
فإن أردت أن تثنى أو تجمع قلت: جاءني ذوا تأبط شرا، وذوو تأبط شرا.
If you wish to dualize or pluralize, you say: 'Jā'anī dhawā Ta'abbat Sharran' (The two Ta'abbat Sharrans came to me), and 'Dhawū Ta'abbat Sharran' (The Ta'abbat Sharrans came to me).
والنسبة إليه تأبطي، تنسب إلى الصدر، ولا يجوز تصغيره ولا ترخيمه.
And the nisbah to him is 'Ta'abbi', attributing to the chest [armpit], and it is not permissible to make it diminutive or elide it.
شربت بجمه وصدرت عنه * وأبيض صارم ذكر إباطى
I drank from its pool and turned away from it * And a sharp, white sword, it mentioned my armpit