When I was younger we spoke it at home as usual, then when my siblings and I started school we started speaking to our parents primarily in English, until soon my mother started speaking to us in English also. So as there was no one around speaking it regularly, I started to forget.
This was fine at first because in London speaking Hausa was not a requirement. I thought I was still fluent till I dated a Hausa guy and we tried having a conversation and to my horror I found myself having to pause and think before coming up with the right words, or asking him to slow down so I could understand better, and finding out that due to the termination of my Hausa speaking in childhood, most of my vocabulary was domesticated and confined to family/home discourses so that a conversation on the presidential election was beyond my capabilities.
I was, however, pleased to note that I could still pronounce certain words correctly, like daya (one) or kara (add) where the 'd' and 'k' is a sharp, implosive sound, or tsaya (stand/stay) where the 's' is pronounced with quick 't' before it. These are all tricks of the tongue that can't be easily taught. There's also the subtle differences with words spelt the same way, like gashi which means hair when the last syllable is low, and 'take this' when it is high.
So a phrase with a double sharp 'd' like 'ga gyada mai dadi,' which I remember young girls chanting in Kaduna as they walked by with a tray full of tins of groundnuts on their heads for sale, would be a challenge for non-native speakers.
Hausa is the most widely spoken language from the Chadic languages group, which in turn is part of the Afro-Asiatic language family where Arabic comes from. This makes it distinct from many other African languages, and rather than the drum-beat influenced sounds of Nigerian languages like Yoruba, Hausa has sharper sounds and spiked parts, and extensive use of 'a' and 'i' vowels as opposed to 'o' and 'u'.
(See more explanations of the Hausa language on Wikipedia here)
The historical connection between Hausa/Fulanis and Arab/Asians extends beyond their common Islamic history. Arabic phrases have become part of the Hausa language, e.g. In sha' Allah which means God willing; and Indian film and music styles are emulated amongst Hausa/Fulanis, as is Henna hand decorations for women which originated in India and Islamic clothing styles and head coverings. The ancestory of the nomadic Fulanis, who have an Arabian appearance and are present in other parts of West Africa as well as Nigeria, have also been traced to Mauritania in North Africa.
People from Mauritania in North Africa
I remember, whilst waiting at a bus stop a while back, hearing the man standing next to me speaking Hausa on the phone. I was amazed! I'd never heard Hausa spoken by a non-family member outside of Nigeria before so I strained to hear him some more and after he ended his call I couldn't resist introducing myself. It was like no matter who he was, we had the Hausa language in common which made him familiar and safe.
I've since made new Hausa friends and they think nothing of speaking to their family and friends in Hausa, but to me, the crisp words are music to my ears and a joyful re-introduction to my history, and as they speaks it's as if my past is unravelled as I remember phrases and words I'd long forgotten.
Speaking Hausa again is like re-discovering something valuable that you lost without knowing when, so that when you find it again you are pleasantly surprised and hold on tighter to it this time around.