Abarim Publications' online Biblical Hebrew Dictionary
The verb אגד ('agad) isn't used in the Bible, but it occurs in Aramaic and in the Talmud, where it means to bind, not merely in the sense of a restrictive binding together of elements but rather in the sense of a fitting together of elements for the proper functioning of the whole.
In the Bible occurs the derived feminine noun אגדה (agudda), meaning band or integrated unit. This word is used for a yoke's thongs (Isaiah 58:6), the mechanism of the heavens (Amos 9:6), and a group of men that forms one unit behind one leader and to one purpose (2 Samuel 2:25; there may be some relation with the noun גדוד (gedud), meaning band of raiders).
This same word is used to describe the item made from hyssop (אזוב, 'ezob) with which the Israelites were to daub the blood of the Pesah lamb on their doors (Exodus 12:22). That means that this item was not simply a bundle or bunch, but rather either a carefully manufactured, possibly interwoven device, or else an item specifically employed to bring about a fitting together for a greater good.
Hyssop was instrumental in cleansing rituals, and such cleaning would allow the cleaned item or person to be reintegrated into society; to rejoin the bond.