Seo libh, . . . . Come on, boys, hurry up literally "here with you, boys, make haste".

a bhuachaillí - - (addressing or calling) "boys" This is the tuiseal gairmeach which has already been explained elsewhere.

An Modh Orduitheach - - The Imperative Mood - - How to give commands:
Déanaigí deifir - - hurry up (An order to more than one person)
Déan deifír - - hurry up (An order to one person)

To give a negative command simply put ná before the verb making no change before a consonant: ná déan deifir - - do not hurry; but put a h before a vowel: ná héist - - do not listen

Éist - - listen; éistígí - - listen (plural); ná héist - - do not listen
Gabh - - accept; gabhaigí - - accept (pl) ná gabh - - do not accept
Múch - - quench; múchaigí - - quench (pl); ná múchaigí - - do not quench
Téigh - - go; téigí - - go (pl); ná téigh - - do not go

Litriú - - Spelling

Have you noticed that some verbs take --aigí for the plural command and others just --igí. This is a spelling rule: caol le caol agus leathan le leathan - - slender with slender and broad with broad. This is important. Vowels before and after a consonant indicate the sound of the consonant. - - i - - and - - e - - are caol - - slender. The other vowels - - a - - o - - u - - and the diphthong - - ae - - are broad. If, in spelling, a slender vowel comes before a consonant or a group of consonants there should be a slender vowel after it also. Similarly - a - o - u - ae - before a consonant should be followed by - - a - - or another broad vowel. I know of only one exception to this rule : ospidéal - - hospital; There is evidence of an inclination to ignore this rule in some composite words nowadays as in mílaois - - the millenium.