Drona is the guru of the Pandavas and the Kauravas. How did he get his name 'Drona'? What is the incident or reason which gave this specific name to him?
Droṇa in Sanskrit means "bucket" (or something like it - not sure of the nuance here). Per the Monier Williams Sanskrit-English Dictionary:
n. (fr. 4. द्रु) a wooden vessel , bucket , trough &c ; a सोम vessel ([cf. Zd. draona]) RV. MBh. &c (ifc. f(आ). Hcat. )
It is said that Drona was born from a bucket, and that that is how he got his name:
And as it came out, he [Bharadwaja] held it in a pot (drana), and of that fluid thus preserved in a pot was born a son who came to be called Drona (the pot-born).
Source: Mahabharata, book 1 (Adi Parva), section 168 (part of the Chaitraratha Parva), using the Ganguli translation.